The invention relates to laser-illuminators used primarily in medical applications.
Lasers can be used to deliver illumination, e.g., diagnostic or therapeutic illumination, to a portion of the body such as a tissue, an organ, or a cavity. An example of therapeutic illumination is photodynamic therapy in which an unactivated agent is administered to a patient and tissue containing the agent is irradiated with light of an appropriate wavelength to activate the agent and kill the illuminated agent-containing tissues.
In photodynamic therapy (PDT), a photosensitizing drug retained in a tissue is excited by an appropriate wavelength light to cause local injury and necrosis of that tissue. Photodynamic action usually requires three components: a photosensitizer, oxygen, and light. Photofrin (PF) is a commonly used photosensitizer. When injected intravaneously, it is taken up and preferentially retained by certain tissues such as neoplastic, inflammatory, traumatized, and embryonic tissues. When excited with light, oxygen inside a cell containing PF converts to singlet oxygen, which results in a toxic effect and cell death. The potential for minimal normal tissue toxicity (because of selective sequestration of PF within tumors) has prompted PDT treatment of skin, bladder, head and neck, brain, and esophageal tumors. Much of the selectivity of PDT is based on vascular uptake, and cell death is due to vascular injury and thrombosis.
The use of PDT for gynecological cancers, although not extensive, has been encouraging. Preferential Photofrin uptake and retention as demonstrated by fluorescence has been reported in both dysplasia and cervical carcinomas. Primary and recurrent vaginal cancers, cervical, and ovarian tumors have been treated by PDT.
The endometrium is a highly vascular tissue that undergoes cycles of neovascularization and thus shares some properties with common solid tumors. Recent discoveries indicate that the endometrium also takes up and retains Photofrin in preference to surrounding tissue including the myometrium.